Measuring instruments, geophysical instruments

Soil Mechanics DIADIM

category:Software Geo&Soft / Soil Mechanics

Design and verifications of sheet-piles and bulkheads

The problem of dimensioning and verifying these structures is solved by Diadim through a finite differences model (FDM) that has been especially designed to evaluate the interaction between soil and structure.
The distribution and magnitude of the loading and resisting forces exerted on the structure are, in fact, greatly influenced by the deformation of the terrain-structure combination, hence it is necessary to use an advanced numerical method that takes into account both the non-linear behaviour of the materials and the time phases of the excavation operations.

The optimisation of the calculation algorithms and the user interface dedicated to specificity of the problem, enable one to analyse and verify quite complex situations with high precision but in extremely very short times.
Given the stratigraphy of the terrain and the position of the aquifer above and below to the work during the different excavation phases, the program calculates the diaphragm as an elastic beam on elasto-plastic supports.
The characteristics and deformability of the terrain are defined in terms of underground modulus that can be defined directly by the user at each stratigraphic level, or, alternatively, can be calculated automatically using different methods based on the geotechnical characterisation of the terrain.

The elastic characteristics of the structure can be explicitly defined in terms of bending stiffness or be automatically calculated on the basis of a description of the section itself; the program can in fact calculate continuous diaphragms in reinforced concrete, beam bulkheads, sheet piles and piles in reinforced concrete.
The user can also choose various constraint conditions of the top and bottom of the diaphragm. The program also enables one to apply external moments and distributed horizontal loads or point loads to the structures.
It is possible to define multiple anchoring levels, that can be schematised as tie rods (possibly pre-stressed) that are only resistant to traction or as rigid braces struts that are also able to absorb compression stresses.

The removal of earth, downhill to the structure, can be divided into different phases, in the numerical simulation. This is an important characteristic of the program as it enables one to take into account the deformations that result from previous excavation phases and to re-calculate the response curve of the terrain downhill to the structure during each excavation phase.

After having calculated the loads on the diaphragm, the program switches to the actual structural analysis phase. The structure is in fact tested for combined compressive and bending stress and, in the case of reinforced piles, the shear resistance due to the reinforcement is verified.

Verification of the moment and normal stress is performed in the section subject to the highest stress using the Ultimate Limit State method, according to Eurocode 2, which takes the mechanical non-linearity of the materials and the non-linearity of the structure into account.

The program determines the bending moment and the normal stress of the calculation and compares these with the ultimate bending moment before failure and the ultimate normal resistive stress, respectively.

The verification of the Shear is performed with the standard method prescribed by Eurocode 2. The program determines the maximum shear force acting on the section and verifies that this is smaller than the bearing capacity of the reinforced concrete beams (Vrd2) and of the reinforcements (Vrd3).